Power conversion system

• US 5,504,667 A
• Filed: 09/07/1994
• Issued: 04/02/1996
• Est. Priority Date: 09/07/1993
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Tadakuma, Susumu, Tanaka, Shigeru
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US08/301,855
• Time in Patent Office: 573 Days
• Field of Search: 363/36, 363/37, 363/39, 363/40, 363/41, 363/45, 363/65, 363/69, 363/95, 363/97, 363/131, 318/800-803, 318/805-810
• US Class Current: 363/37
• CPC Class Codes: H02M 5/4505 having a rectifier with controlled elements
• CPC Class Codes: H02M 7/162 in a bridge configuration
• CPC Class Codes: H02P 21/00 Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation

Abstract

A power conversion system including a single-phase AC power source for generating an AC power. The power conversion system further includes an AC/DC power converter connected to the single-phase AC power source for converting the AC power into a DC power, a main smoothing capacitor connected to DC terminals of the AC/DC power converter, a DC active filter connected in parallel with the main smoothing capacitor for controlling a compensation current flowing in the DC active filter such as to absorb an amount of fluctuation of the AC power supplied from the single-phase AC power source, and a load device connected to the main smoothing capacitor as a DC voltage source for receiving a first DC voltage applied to the main smoothing capacitor.

Claims

1. A power conversion system, comprising:

a single-phase AC power source for generating an AC power;

an AC/DC power converter connected to said single-phase AC power source for converting said AC power into a DC power;

a main smoothing capacitor connected to DC terminals of said AC/DC power converter;

a DC active filter connected in parallel with said main smoothing capacitor for controlling a compensation current (IF) flowing in said DC active filter such as to absorb an amount of fluctuation of said AC power supplied from said single-phase AC power source; and

a load device connected to said main smoothing capacitor as a DC voltage source for receiving a first DC voltage (Vd) applied to said main smoothing capacitor.

2. The power conversion system according to claim 1, wherein said DC active filter includes:

a DC constant voltage source for generating a second DC voltage;

a voltage source PWM inverter connected to said DC constant voltage source for converting said second DC voltage into a variable-voltage AC voltage;

a single-phase transformer connected to AC side output terminals of said voltage source PWM inverter; and

a DC smoothing capacitor connected in series with a secondary winding of said single-phase transformer;

said compensation current (IF) flowing through said DC smoothing capacitor.

3. The power conversion system according to claim 1, wherein said DC active filter includes:

a DC constant voltage source for generating a second DC voltage;

a voltage source PWM inverter connected to said DC constant voltage source for converting said second DC voltage into a variable-voltage AC voltage; and

a series circuit of a DC smoothing capacitor and an inductor, said series circuit being connected in series with AC side output terminals of said voltage source PWM inverter;

said compensation current (IF) flowing through said series circuit.

4. The power conversion system according to claim 1, wherein said DC active filter includes:

a DC constant current source for generating a DC current;

a current source PWM inverter connected to said DC constant current source for converting said DC current into a variable-current AC current;

a high frequency capacitor connected to AC output terminals of said current source PWM inverter; and

a DC smoothing capacitor connected in series with said high frequency capacitor;

said compensation current (IF) flowing through said DC smoothing capacitor.

5. The power conversion system according to claim 1, wherein said DC active filter includes:

a DC constant current source for generating a DC current;

a current source PWM inverter connected to said DC constant current source for converting said DC current into a variable-current AC current;

a high frequency capacitor connected to AC output terminals of said current source PWM inverter;

a single-phase transformer connected in parallel with said high frequency capacitor; and

a DC smoothing capacitor connected in series with a secondary winding of said single-phase transformer;

said compensation current (IF) flowing through said DC smoothing capacitor.

6. The power conversion system according to claim 1, wherein said DC active filter includes:

a high frequency voltage source for supplying a high frequency voltage;

a circulating current type cycloconverter connected to receive said high frequency voltage as an input for generating a single-phase AC voltage; and

a DC smoothing capacitor connected in series with output terminals of said circulating current type cycloconverter;

said compensation current (IF) flowing through said DC smoothing capacitor.

7. The power conversion system according to one of claims 2 to 6:

wherein a capacitance of said DC smoothing capacitor of said DC active filter is larger than a capacitance of said main smoothing capacitor.

8. The power conversion system according to claim 1:

wherein said DC active filter controls said compensation current (IF) in response to a difference of a first DC current (Id1) outputted by said AC/DC power converter and a second DC current (Id2) fed into said load device.

9. The power conversion system according to claim 1:

wherein said DC active filter controls said compensation current (IF) in response to a difference of a calculated value (Pc) of an AC instantaneous power of said AC/DC power converter and a calculated value (Pav) of a mean active power supplied from said single-phase AC power source.

10. The power conversion system according to claim 1:

wherein said AC/DC power converter includes a PWM converter for controlling an input current (Is) supplied from said single-phase AC power source such that said first DC voltage (Vd) applied to said main smoothing capacitor is practically constant.

11. The power conversion system according to claim 10;

wherein a command value (IF*) for said compensation current (IF) of said DC active filter is given as;

space="preserve" listing-type="equation">IF*=(k1·

ec*·

Is*-k2·

Vsm·

Ism*)/Vd

where a voltage command value of said PWM converter is ec*, an input current command value of said PWM converter is Is*, a peak value of said input current command value (Is*) of said PWM converter is Ism*, a peak value of an output voltage (Vs) of said single-phase AC power source is Vsm, a detection value of said first DC voltage of said main smoothing capacitor is Vd, and proportionality constants are k1 and k2.

12. The power conversion system according to claim 10:

wherein, when said input current (Is) supplied from said single-phase AC power source and an output voltage (Vs) of said single-phase AC power source are controlled to be in-phase sine waves by said PWM converter, a command value (IF*) for said compensation current (IF) of said DC active filter is given as;

space="preserve" listing-type="equation">IF*=-Ism·

Vcm/(2·

Vd)·

cos (2ω

t-θ

) (during power running), and

space="preserve" listing-type="equation">IF*=+Ism·

Vcm/(2·

Vd)·

cos (2ω

t-θ

) (during regenerative operation)

where

space="preserve" listing-type="equation">VLsm=ω

·

Ls·

Ism

space="preserve" listing-type="equation">Vcm=(Vsm.sup.2 +VLsm.sup.2).sup.1/2

space="preserve" listing-type="equation">θ

=tan.sup.-1 (VLsm/Vsm)

and, where a peak value of said output voltage (Vs) of said single-phase AC power source is Vsm, a peak value of said input current (Is) of said PWM converter is Ism, and a detection value of said first DC voltage of said main smoothing capacitor is Vd.

13. The power conversion system according to claim 10:

wherein, when said input current (Is) supplied from said single-phase AC power source is controlled to be a sine wave with lagging phase angle φ

with respect to an output voltage (Vs) of said single-phase AC power source by said PWM converter, a command value (IF*) for said compensation current (IF) of said DC active filter is given as;

space="preserve" listing-type="equation">IF*=-Ism·

Vcm/(2·

Vd)·

cos (2ω

t-θ

-φ

) (during power running), and

space="preserve" listing-type="equation">IF*=+Ism·

Vcm/(2·

Vd)·

cos (2ω

t-θ

-φ

) (during regenerative operation)

where

space="preserve" listing-type="equation">Ism=(IPm.sup.2 +IQm.sup.2).sup.1/2

space="preserve" listing-type="equation">φ

=tan.sup.-1 (IQm/IPm)

space="preserve" listing-type="equation">VcP=Vsm-ω

·

Ls·

IQm

space="preserve" listing-type="equation">VcQ=-ω

·

Ls·

IPm

space="preserve" listing-type="equation">Vcm=(VcP.sup.2 +VcQ.sup.2).sup.1/2

space="preserve" listing-type="equation">θ

=tan.sup.-1 (VcQ/VcP)

and, where a peak value of said output voltage (Vs) of said single-phase AC power source is Vsm, a peak value of said input current (Is) of said PWM converter is Ism, an active component of said peak value (Ism) is IPm, a reactive component of said peak value (Ism) is IQm and a detection value of said first DC voltage of said main smoothing capacitor is Vd.

14. The power conversion system according to claim 1, wherein said load device includes:

a PWM inverter connected to said main smoothing capacitor for converting said first DC voltage (Vd) into a three-phase AC voltage, and

a three-phase induction motor driven by said PWM inverter.

15. A power conversion system, comprising:

a single-phase AC power source for generating an AC power, wherein the frequency of fluctuation of said AC power is twice that of the frequency of said AC power source;

an AC/DC power converter connected to said single-phase AC power source for converting said AC power into a DC power;

a main smoothing capacitor connected to the DC terminals of said AC/DC power converter;

a DC active filter connected in parallel with said main smoothing capacitor for controlling a compensation current (IF) flowing in said DC active filter such as to absorb an amount of fluctuation of said AC power supplied from said single-phase AC power source;

a load device connected to said main smoothing capacitor as a DC voltage source for receiving said first DC voltage (Vd) applied to said main smoothing capacitor; and

said AC/DC power converter further comprising a PWM converter for controlling an input current (Is) supplied from said single-phase AC power source such that said first DC voltage (Vd) applied to said main smoothing capacitor is practically constant.